1. Field of the Invention
The present invention relates to document processing machines and, more particularly, to document processing machines adapted to color printing.
2. Prior Art
Referring to FIG. 1, there is shown a perspective view of a document processed apparatus 5. The apparatus 5 could be any suitable type of document processing apparatus, such as a copier, a facsimile machine, a scanner, or a computer printer adaptable to color processing and printing on a printable substrate.
One specific application of color processing is customer selectable color printing, wherein a very specific color is required. Customer selectable colors are typically utilized to provide instant identification and authenticity to a document. As such, the customer is usually concerned that the color meets particular color specifications. For example, the red color associated with the XEROX™ digital stylized “X” is a customer selectable color having a particular shade, hue and color value. Likewise, the particular shade of orange associated with Syracuse University is a good example of a customer selectable color. A more specialized example of customer selectable color output can be found in the field of custom color, which specifically refers to registered proprietary colors, such as used, for example, in corporate logos, authorized letterhead and official seals. The yellow associated with KOKAK™ brand products, and the brown associated with HERSHEY™ brand products are good examples of exacting custom colors which may be required in a highlight color or spot color printing application. However, the various colors typically utilized for standard highlighting processes generally do not precisely match customer selectable colors. Moreover, customer selectable colors typically cannot be accurately generated via halftone process color methods because the production of solid image areas of a particular color using halftone image processing techniques typically yields non-uniformity of the color in the image area. Further, lines and text produced by halftone process color are very sensitive to mis-registration of the multiple color images such that blurring, color variances, and other image quality defects may result.
As a result of the deficiencies noted above, customer selectable color production in electrostatographic printing systems is typically carried out by providing a singular premixed developing material composition (e.g., ink) made up of a mixture of multiple color toner particles blended in preselected concentrations for producing the desired customer selectable color output. This method of mixing multiple color toners to produce a particular color developing material is analogous to processes used to produce customer selectable color paints and inks. In offset printing, for example, a customer selectable color output image is produced by printing a solid image pattern with a premixed customer selectable color printing ink as opposed to printing a plurality of halftone image patterns with various primary colors or compliments thereof. This concept has generally been extended to electrostatographic printing technology, as disclosed, for example, in commonly assigned U.S. Pat. No. 5,557,393, wherein an electrostatic latent image is developed by a dry powder developing material comprising two or more compatible toner compositions to produce a customer selectable color output.
Customer selectable color printing materials including paints, printing inks and developing materials can be manufactured by determining precise amounts of constituent basic color components making up a given customer selectable color material, providing precisely measured amounts of each constituent basic color component and thoroughly mixing these color components. This process is commonly facilitated by reference to a color guide or swatch book containing hundreds or even thousands of swatches illustrating different colors, wherein each color swatch is associated with a specific formulation of colorants. Probably the most popular of these color guides is published by Pantones®, Inc. of Moonachie, N.J. The Pantone® Color Formula Guide expresses colors using a certified matching system and provides the precise formulation necessary to produce a specific customer selectable color by physically intermixing predetermined concentrations of up to four colors from a set of up to 16 principal or basic colors.
There are many colors available using the Pantone® system or other color formula guides of this nature that cannot be produced via typical half tone process color methods. In the typical operational environment, an electrostatographic printing system may be used to print various customer selectable color documents. To that end, replaceable containers of premixed customer selectable color developing materials corresponding to each customer selectable color are provided for each print job. Replacement of the premixed customer selectable color or substitution of another premixed color between different print jobs necessitates operator intervention and print job halts, among other undesirable requirements. Also, since each customer selectable color is typically manufactured at an off-site location, supplies of each customer selectable color printing ink must be separately stored and inventoried for each customer selectable color print job.
In addition, it is known that properties of the printable substrate also affects the color of the print. Many paper substrates are slightly off-white in the direction of blue or green or yellow. Such paper tint can shift the print color away from the customer-selected color, even though the developed ink layer is maintained exactly at its specified value. It is further known that the reflectivity of the substrate also effects the print color. More reflective substrates may result in color with higher gloss, higher brightness and higher measured color saturation then might otherwise be desired.